1. Statement of the Technical Field
The inventive arrangements relate generally to the field of energy storage, and more particularly to an energy storage device incorporated onto substrate materials.
2. Description of the Related Art
Shrinking geometries and increasing clock speeds have consistently driven down the supply voltages for central processing units (CPUs), digital signal processors (DSPs), and other printed circuit board devices. Currently these devices can operate in the +1.0V to +2.0V range, but operational voltages will decrease further as operational frequencies and circuit component densities continue to increase. Efficient power generation at low voltages can be a problem, however, especially when supplying power to modern circuit devices that require tight voltage regulation and draw high levels of current.
Circuit voltage drops is one obstacle to providing tight voltage regulation in modern circuits. In particular, as the current a circuit device draws from a power supply increases, the voltage drop across the circuit increases proportionally (Vdrop=IR). For example, if a device requiring a 1.5V supply voltage is mounted on a circuit board having a circuit resistance of 20 mxcexa9, the voltage drop across the circuit is 0.04V when 2A of current is drawn by the device. However, if the current draw for the same device increases to 20A, the voltage drop across the circuit increases to 0.4V. Accordingly, the voltage available at the power input to the circuit device is only 1.1V, which may be lower than the input voltage needed for the device to properly operate.
Moreover, line inductance also can adversely affect current flow across the circuit. Specifically, the line inductance can adversely affect the step response and the impulse response of the circuit by reducing the slew rate. Hence, when a circuit device requires a sudden increase in current, it will generally take a moment (rise time) for the current to reach the required level, thereby starving the circuit device for current until the required current level is reached.
To reduce the slew rate and voltage drop experienced in a circuit while still providing high values of current to circuit devices, circuit designers commonly include capacitors on printed circuit boards. In operation, the capacitors store energy during parts of circuit device""s duty cycle when the circuit device has low to moderate current requirements. Then, when the circuit device requires a high level of current, the energy stored in the capacitors can be used to supplement the current provided by the power supply. Once the high current demand subsides, the capacitors can recharge. Using the above example, if the capacitors can supply 70% of the circuit device""s 20A requirement, only 6A of current will be supplied by the power supply, hence the voltage drop across the circuit reduces to 0.12V. Accordingly, the voltage at the devices power input is 1.38V, which is probably within the operational tolerance of a 1.5V circuit device.
Importantly, the capacitors typically have relatively high values of capacitance so that the capacitors can store enough energy to supply adequate levels of current. In consequence, capacitors that are used to supplement supply current tend to be fairly large. In order to minimize the slew rate and voltage between the capacitors and the circuit device having the high current requirements, the capacitors also are usually located near the circuit device to minimize circuit resistance and inductance between the capacitors and the circuit device. Locating large capacitors on a printed circuit board at the proper location often can be challenging, however. In particular, the capacitors can limit the extent to which the size of a circuit board can be reduced. Moreover, the capacitors can interfere with the mating of the circuit board to other devices.
The present invention relates to a micro-electromechanical homopolar generator on a substrate and a method of manufacturing the same. The micro-electromechanical homopolar generator includes first substrate layer, which has an axial rotor contact portion and a radial edge portion concentric with, and radially spaced from, the axial rotor contact portion. The rotor contact portion and the radial edge portion provide electrically isolated first and second conductive contacts respectively proximate to each of the axial rotor contact portion and the radial edge portion. The first substrate layer also includes an axial contact brush and a radial edge brush respectively coupled to the first and second conductive contacts.
At least one conductive disc is axially aligned with the axial rotor contact portion and a peripheral edge of the conductive disc is proximate the radial edge portion. Accordingly, the axial contact brush and the radial edge brush respectively form an electrical contact with an axial portion and a peripheral edge portion of the conductive disc. The micro-electromechanical homopolar generator also includes at least one magnet spaced from at least one of an opposing upper and lower surface of the conductive disc to define a magnetic field aligned with an axis of rotation of the conductive disc. The magnet can be selected from the group consisting of an electromagnet and a permanent magnet. In the case that an electromagnet is included, means can be provided to adjust electric current through the electromagnet, wherein an adjustment of the electric current adjusts a strength of the magnetic field.
The substrate can be any substrate material suitable for a micro-electromechanical manufacturing process, for example a ceramic substrate or a semiconductor substrate. A second substrate layer can be provided over the first substrate layer to define a bearing surface for the conductive disc. A seal layer can be disposed on the second ceramic substrate layer, forming a continuous seal around a periphery of the conductive disc. A lid can be suspended on the seal layer, extending over the conductive disc, and a first magnet may be attached to the lid. A third substrate layer can be disposed on a surface of the first substrate opposed from the conductive disc for supporting a second magnet.